Many municipalities, states and countries may require smoke alarms through building codes, e.g., 2012 International Residential Code (IRC), in each sleeping room, outside each separate sleeping area in the immediate vicinity of the bedrooms, and on each additional story of the dwelling, including basements (IRC 314.3). Smoke detectors may be powered from the AC line and may have a battery backup. A single backup battery may be provided for a plurality of smoke detectors, e.g., in industrial installations where the one main battery backup may be used instead of a backup battery at each smoke alarm.
Where more than one smoke alarm is required to be installed within an individual dwelling unit in accordance with IRC Section R314.3, the smoke alarm devices shall be interconnected in such a manner that the actuation of one smoke alarm will activate all of the smoke alarms in the individual unit (IRC 314.5). The National Fire Protection Association (NFPA) recommends that smoke alarms be tested one a month. Even better to test once a week. However, testing of smoke alarms requires activating a test button on the smoke alarm device that, generally, is mounted on a ceiling of a room and well out of reach of a person unless a ladder or chair is used by the person to reach the smoke alarm test button. Even if the smoke alarm test button is easily reachable, the audible alarm signal is uncomfortable to the ears at close range.